Process for producing permanent magnets



Patented June 1, 1937 UNITED STATES.

PROCESS Q FOR PRODUCING PERMANENT MAGNETS cum s. Williams, Forest Hills, Pa, assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation 01' Pennsylvania No Drawing. Application May 8, 1935,

Serial No. 20,437

6 (Cl. Ida-13 substantially iron. The alloy is heated at a tem- Y This invention relates to a process of heat treating for improving the magnetic properties of permanent magnets.

' An object of this invention is to provide for improving the magnetic properties of magnetic material. I

Another object of this invention is to provide a heat treatment 'i'or magnetic alloys capable of being age hardened, that will so homogenize the material that its magnetic properties may be improved. I In practicing thisinvention, repeated cycles of similar heat treatments are provided for magnetic alloys so that the alloying elements will be dispersed throughout the alloy and.the magnetic properties of the alloy may be improved.

In the preferred embodiment of this invention, the first cycle heat treatment comprisessubjecting the alloys whichare capable of being age hardened to a temperature of from 1100 to 1350 C., and quenching from that temperature. The quenching medium may be oil, water or air.

Alter quenching the alloy is heated to and held 30 the magnetic properties or the alloy may be improved. v r.

In practice, the second cycle of the heat treat- .ment is similar to the homogenizing treatment in that the alloy is subjected to a temperature of 35 between l100 to 1350 C. and quenched. In order to set up the desired fine dispersion of the alloying elements, the quenched alloy is aged at a temperature of between 550 and-700 C. The alloys are subjected to the annealing and ageing temperatures for different periods of time depending upon the composition of the alloy treated and th size of the castings so heat treated.'

This process is employed primarily to develop the magnetic properties of alloys which are capable 0! being age hardened such as iron cobalt alloys comprising from about 2% to 80% cobalt and from 2% to 35% of other alloying elements with the balance substantially iron. Alloys comprising iron, cobalt and either tungsten or molybdenum in which manganese may or may not be present are particularly benefited by this heat treatment.

The beneficial efiect of this heat treatment is pronounced when applied to an alloy comprising 12% cobalt, 19% molybdenum with. the balance Derature of 1300 'C. for at least ten minutes and quenched in oil from that temperature. The quenched alloy is then subjected to an ageing temperature of about 700 C. forat least onehalfhour and preferably from one to two hours. This cycle of heat treatment so homogenizes the alloy that when subjected to another cycle oi a similar heat treatment, its magnetic properties will be fully developed.

In the second cycle of the heat treatment the homogenized alloy is reheated to a temperature of 1300? C. for at least ten minutes and then quenched in oil. After the quenching is eilected,

the alloy is aged at a temperature of 650 C. for

a period of from 1 to 3 hours. This cycle completes the heat treatment in that it is found that the desired precipitation or age hardening of the homogenized alloy is eflfected. In order that the .precipitation may be closely controlled, the ageing temperature of the second cycle of the heat treatment is usually lower than that of the first cycle.

When the iron, cobalt and molybdenum alloy hereinbetore identified is subjected to the heat Br. (Gausses) As quenched from 1300 C 6700 As aged at 700 C 8000 As quenched from 1300 C.. 5100 As aged at 650 C 9400 An examination of these results shows the increase in remanence values through the application of the two cycles of heat treatment, The remanence value is increased about 17% by the second cycle of heat treatment.

Although this invention has been described with reference to an iron, cobalt and molybdenum alloy, it is to be understood that it is not to be limited thereto, but is applicable to any .of the permanent magnet alloys which are capable of being age hardened. Further, it is to be noted that the specific heat treatments described are capable of many modifications therein as tothe temperatures employed and 'the length of time of each of the quenching and ageing periods and that this invention is therefore not to be limited except insofar as is necessitated by the prior art and the scope of the appended claims.

I claim as my invention:

1. In the process of producing pe nent magnets, in combination, quenching %Znetic material from e. temperature above 11 C, ageing the quenched material at a temperature of about 700 C. to homogenize it, reheating the homogenized material to a temperature above 1100 'C., quenching the material, and ageing the quenched material at a temperature of about 650 C. to develop its magnetic properties.

2. In the process of producing permanent mag nets from age hardening alloys, in combination,

quenching the alloy from a temperature above" 1100 C., ageing the quenched alloy ate. temperature of between 600 and 800 C. to homotemperature above 1100 C quenching the alloy,

and ageing the alloy at a temperature of between 550 and 700 C.

3. In the process of producing permanent mag- Xhets from age hardening alloys, in combination,

nets from age hardening alloys, in combination, quenching the alloy from a temperature of about 1300 C, ageing the quenched alloy at a temperature of about 700 C. to homogenize it,-reheating the homogenized alloy at a temperature of about 1300 C., quenching the alloy, and ageing the alloy at a temperature of about 650 C.

5. In the process of producing permanent mag nets from age hardening alloys, in combination, quenching the alloy in oil from a temperature of about 1300 C., ageing the quenched alloy at a temperature or about 700 C., reheating the alloy at a temperature of about 1300" 0., quenching the ailoy in oil, and ageing the alloy at a temperature of about 650 0. genize it, reheating the homogenized alloy at a 6. In the process of producing permanent magnets from an alloy comprising about 12% cobalt, about 19% molybdenum with the balance sub stantially iron, in combination, heating the alloy at a temperature of between 1250" and 1850 C. for at least ten minutes, quenching the alloy in oil, heating the quenched alloy at a temperature of about 700 C. for. at least one-half hour, reheating the alloy at a temperature of between 1250 and 1350 C., for at least 10 minutes, quenching the reheated alloy in oil, ageing the alloy at a temperature 011 about 650 C. for at least one hour, and cooling the alloy to room temperature.

CUFION awmums. 

